Aldose reductase (also known as alditol: NADP+1-oxidoreductase) reduces aldose sugars to polyols and has been implicated as a primary factor in diabetic complications such as cataracts, retinopathy and neuropathy. cDNA clones for aldose reductase have been isolated and are now being characterized. A bovine retina Lambdagt11 expression vector library was screened using antisera against rat lens aldose reductase. Several presumtive aldose reductase cDNA clones, approximately 300 base pairs in size, have been identified. Southern blot analysis determined that these cDNA clones are not homologous. One cDNA insert was cleaved by EcoRI restriction enzyme and purified by gel electrophoresis and subcloned into an M13 sequencing vector for DNA sequence determination. The DNA sequence for this cDNA insert revealed that there are no homologous sequences to known DNA sequences listed in the Genetic Sequence Data Bank. Using this sequenced cDNA and the other non-homologous 300 base pair cDNA clones, we plan to isolate and sequence larger cDNA fragments to obtain the entire coding region. Northern blot analysis indicates that the messenger RNA for aldose reductase is about 2 kilobases in size, suggesting a large untranslated region since the protein has a molecular weight of approximately 37,000. One of our goals is to utilize the structural data obtained from the nucleotide sequence to selectively inhibit the aldose reductase gene in target cells. In addition, we plan to investigate the level of gene expression of aldose reductase in experimentally-induced diabetic and galactosemic animals.